Synthesis of an optically active poly(aryleneethynylene) bearing galvinoxyl residues and its chiroptical and magnetic properties

We synthesized an optically active poly(binaphthyl-6,6′-diylethynylene-1,3-phenyleneethynylene) with pendant galvinoxyl residues. The hydrogalvinoxyl precursor polymer was given by polymerization of (1,3-diiodophenyl)hydrogalvinoxyl and 6,6′-diethynyl-2,2′-dihexyloxybinaphthyl using Pd(PPh3)4 catalyst (Mw = 4.6 × 104, Mw/Mn = 3.0). The polymer yielded the corresponding polyradical with high spin concentration by treatment of the polymer solution with PbO2. In the CD spectra of the polymer and polyradical taken in various solutions, clear Cotton effects were observed in the absorption region of the binaphthyl chromophore, while no Cotton effect was observed in that of the galvinoxyl chromophore. On the other hand, in the MCD, Faraday effects were observed in the absorption region of the backbone and galvinoxyl chromophore. The static magnetic susceptibility of the chiral polyradical was measured using a SQUID magnetometer, and showed weak antiferromagnetic interaction.